The principles on which the present apparatus is based are well known in the prior art. For instance, the concept of making a treatment plant using aeration to sustain the bacterial digestion of wastes for small communities has been extensively discussed in a 1966 publication of the National Sanitation Foundation of Ann Arbor, Michigan, entitled "Package Plant Criteria Development" based on a study made for the Federal Water Pollution Control Administration, Demonstration Grant Project WPD-74. Moreover, the concept of bubbling air through the sewage in a manner to make it circulate is known in the prior art as evidenced by U.S. Pat. Nos. 3,348,687 to Foster; 3,627,136 to Mackre and 3,809,245 to Kennedy, these patents using such circulation to promote centrifugal separation of solid particles from the sewage so that relatively clearer water can be removed as an effluent.